Re: [PATCH v3 01/12] usb: xhci: add sysfs file for xHCI debug port

[Lu, Baolu]

On 11/10/2015 05:36 PM, Dave Young wrote:
> [snip]
>
> > diff --git a/drivers/usb/host/xhci-sysfs.c b/drivers/usb/host/xhci-sysfs.c
> > new file mode 100644
> > index 0000000..0192ac4
> > --- /dev/null
> > +++ b/drivers/usb/host/xhci-sysfs.c
> > @@ -0,0 +1,100 @@
> > +/*
> > + * sysfs interface for xHCI host controller driver
> > + *
> > + * Copyright (C) 2015 Intel Corp.
> > + *
> > + * Author: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
> > + *
> > + * This program is free software; you can redistribute it and/or modify
> > + * it under the terms of the GNU General Public License version 2 as
> > + * published by the Free Software Foundation.
> > + */
> > +#include <linux/kernel.h>
> > +
> > +#include "xhci.h"
> > +
> > +/*
> > + * Return the register offset of a extended capability specified
> > + * by @cap_id. Return 0 if @cap_id capability is not supported or
> > + * in error cases.
> > + */
> > +static int get_extended_capability_offset(struct xhci_hcd *xhci,
> > +					int cap_id)
> > +{
> > +	u32		cap_reg;
> > +	unsigned long	flags;
> > +	int		offset;
> > +	void __iomem	*base = (void __iomem *) xhci->cap_regs;
> > +	struct usb_hcd	*hcd = xhci_to_hcd(xhci);
> > +	int		time_to_leave = XHCI_EXT_MAX_CAPID;
> > +
> > +	spin_lock_irqsave(&xhci->lock, flags);
> > +
> > +	offset = xhci_find_next_cap_offset(base, XHCI_HCC_PARAMS_OFFSET);
> > +	if (!HCD_HW_ACCESSIBLE(hcd) || !offset) {
> > +		spin_unlock_irqrestore(&xhci->lock, flags);
> > +		return 0;
> > +	}
> > +
> > +	while (time_to_leave--) {
> > +		cap_reg = readl(base + offset);
> > +
> > +		if (XHCI_EXT_CAPS_ID(cap_reg) == cap_id)
> > +			break;
> > +
> > +		offset = xhci_find_next_cap_offset(base, offset);
> > +		if (!offset)
> > +			break;
> > +	}
> > +
> > +	spin_unlock_irqrestore(&xhci->lock, flags);
> I'm not sure spin_lock is good and necessary here, also seems there's already

The lock is unnecessary here. I will remove it.

> a function to find the cap offset:
> xhci_find_ext_cap_by_id() in xhci-ext-caps.h

Yes, I will refactor the code.

Thanks,
Baolu
> > +
> > +	return offset;
> > +}
> > +
> Thanks
> Dave

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